1. Field of the Invention:
The present invention relates to a multicolor fluid jet loom which in operation carries out a cutting blow, and more particularly, to a device for preventing the cutting of a weft yarn which need not be cut on such a multicolor fluid jet loom.
2. Description of the Prior Art:
In a multicolor fluid jet loom, a plurality of weft yarns are picked sequentially in a predetermined order, and the picked weft yarn is cut with a cutter provided on the picking side of the multicolor fluid jet loom. While the picked weft yarn is cut with the cutter, the free ends of the rest of the weft yarns, namely, the standby weft yarns, are extending outside of their corresponding picking nozzles. In case the free end of the standby weft yarn nears the picked weft yarn, the cutter erroneously cuts the free end of the stanby weft yarn. As a result, the free end of the thus cut standby weft yarn is blown towards a shed of a warp yarn by a cutting blow and inserted into a fabric.
The term "cutting blow" refers to a cutting blow system provided with multicolor fluid jet looms. The cutting blow is a small amount of fluid which is continuously jetted from a picking nozzle during the period of operation of the jet loom other than a picking period. Alternatively, a small amount of fluid may be jetted from the picking nozzle just before an/or just after a cutting operation. These small jets of fluid ensure that a picked weft yarn is extended and prevented from slipping off of or being extracted from its picking nozzle after the picked weft yarn has been cut by the cutter. Faulty cutting occurs frequently when hard yarns, such as hard twist yarns or glass yarns, are used as weft yarns. When such stiff yarns are used as weft yarns, the fluid is jetted continuously at a moderate rate from the picking nozzles to prevent the standby weft yarns from slipping off from the picking nozzles. The free end of the hard twist yarn is untwisted and extended by the jet of fluid to enter the operating zone of the cutter. When the glass yarn is used as a weft yarn, a portion of the picked glass yarn is slackened between the weft yarn storage device and the cutter used to cut the glass yarn, because the glass yarn is stiff. Then, a slack free end of a standby glass yarn is extended by the fluid being continously jetted from the picking nozzle and thereby the free end of the standby glass yarn reaches the cutting position of the cutter entailing erroneous weft yarn cutting. Accordingly, the multicolor fluid jet loom must be equipped with a standby weft yarn cutting prevention device.
Japanese Utility Model Publication No. 51-5570 discloses a weft yarn withdrawing device, which withdraws the free end of the standby weft yarn with a lever from the picked weft yarn to avoid the entanglement of the free end of the standby weft yarn with the picked weft yarn. This known weft yarn withdrawing device is capable of surely preventing erroneous weft yarn cutting. Nevertheless, the weft yarn withdrawing device is a complicated mechanism and inevitably applies an excessive tension to the weft yarn in withdrawing the weft yarn by hooking the weft yarn with the lever, often damaging the weft yarn. Thus, the weft yarn withdrawing device is not an effective solution of the problem from the viewpoint of maintaining the quality of the fabric.